The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Referring now to FIGS. 1A and 1B, a DC-to-DC converter (hereinafter converter) 100 is shown. In FIG. 1A, the converter 100 includes a control module 102, a dead time control module 103, a high-side switch THS, a low-side switch TLS, an inductor L, a capacitor Cout, and a load 104. The high-side switch THS and the low-side switch TLS (collectively switches) are connected in series. The control module 102 generates PWM pulses that control on and off times of the switches. The dead time control module 103 controls dead times of the switches (explained below). The inductor L is connected to a junction of the switches and is connected in series with the capacitor Cout as shown. The load 104 is connected in parallel to the capacitor Cout as shown. The converter 100 receives an input voltage Vdd and outputs an output voltage Vout across the load 104.
In FIG. 1B, an inductor current IL increases when the high-side switch THS is turned on while the low-side switch TLS is turned off and decreases when the high-side switch THS is turned off while the low-side switch TLS is turned on. A voltage VLX at the junction of the switches varies with time t as shown in FIG. 1B. A time interval between opening (i.e., turning off) one switch (e.g., the high-side switch THS) and closing (i.e., turning on) another switch (e.g., the low-side switch TLS) is called a dead-time and is shown by dotted circles in FIG. 1B. Body diodes DHS and DLS, which are respectively integrated with the high-side switch THS and the low-side switch TLS, conduct during dead times causing power loss. Power loss also occurs due to reverse recovery. Power losses due to conduction of the body diodes and reverse recovery are pronounced at high switching frequencies of the PWM pulses and low output voltages (Vout) of the converter. The dead times therefore need to be minimized to reduce the power losses.
Referring now to FIGS. 2A-2C, different modes of operation of a converter and corresponding dead times are shown. For example, in FIG. 2A, the converter operates in a Buck continuous conduction mode (CCM) with a heavy load, where the inductor current IL is always positive. In FIG. 2B, the converter operates in a Buck or Boost forced CCM with a light load, where the inductor current IL can be positive and negative. In FIG. 2C, the converter operates in a Boost CCM with a heavy load, where the inductor current IL is always negative. In each mode, the dead times shown need to be minimized to reduce the power losses.